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CAMBRIDGE INTERNATIONAL EXAMINATIONS
9702 PHYSICS
9702/51
Paper 5 (Planning, Analysis and Evaluation),
maximum raw mark 30
This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of
the examination. It shows the basis on which Examiners were instructed to award marks. It does not
indicate the details of the discussions that took place at an Examiners’ meeting before marking began,
which would have considered the acceptability of alternative answers.
Mark schemes should be read in conjunction with the question paper and the Principal Examiner
Report for Teachers.
Cambridge will not enter into discussions about these mark schemes.
Cambridge is publishing the mark schemes for the May/June 2014 series for most IGCSE, GCE
Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.
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MARK SCHEME for the May/June 2014 series
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GCE Advanced Subsidiary Level and GCE Advanced Level
Page 2
1
Mark Scheme
GCE AS/A LEVEL – May/June 2014
Syllabus
9702
Paper
51
Planning (15 marks)
Defining the problem (3 marks)
P
r is the independent variable or vary r.
[1]
P
T (or t) is the dependent variable or measure T (or t).
[1]
P
Keep the radius of curvature (of the track) or C constant (or radius of track
constant). Do not allow “use same track”.
[1]
Methods of data collection (5 marks)
M
M
M
M
M
Diagram showing ball in a (curved) track with supports for track, e.g. retort
stands. Minimum of two labels (from ball, track, supports; not stopwatch, bench,
micrometer).
Supports making contact with track higher than ball / at least half way up.
[1]
Measure time using stopwatch or light gates and timer or datalogger with motion
sensor.
Detail needed for video camera.
[1]
Use many oscillations (at least 10 or at least 10 s of timing) and determine
T = t / n.
[1]
Measure diameter (radius) of ball with a micrometer / vernier calipers.
Do not allow travelling microscope.
[1]
radius = diameter / 2.
[1]
Method of analysis (2 marks)
A
A
Plot a graph of T 2 against r (or r against T 2)
Do not allow log graphs.
5g
y − intercept
(or for r against T 2, C = y-intercept)
C = y-intercept ×
=
2
gradient
28π
[1]
[1]
Safety considerations (1 mark)
S
Precaution linked to ball escaping on to floor, e.g. use barrier / safety
screen / sand tray to prevent balls rolling on to floor.
© Cambridge International Examinations 2014
[1]
Page 3
Mark Scheme
GCE AS/A LEVEL – May/June 2014
Syllabus
9702
Paper
51
Additional detail (4 marks)
D
1
2
3
4
5
6
7
8
Relevant points might include
Add weights to / G-clamp retort stands
Keep the material / density of the ball constant
Use of fiducial marker near centre of track / mark on the track
Clean track / balls. Do not allow oil the track.
Repeat measurements of t (for each ball) and average
Repeat measurement for d (or r) and average
Relationship is valid if straight line, provided plotted graph is correct
Relationship is valid if straight line not passing through origin or has an intercept,
provided plotted graph is correct (any quoted expression must be correct, e.g.
28 π 2C
)
y-intercept =
5g
[4]
Do not allow vague computer methods.
[Total: 15]
© Cambridge International Examinations 2014
Page 4
2
Mark Scheme
GCE AS/A LEVEL – May/June 2014
Syllabus
9702
Paper
51
Analysis, conclusions and evaluation (15 marks)
Mark
Expected Answer
(a)
A1
gradient = –R
y-intercept = –R/P
(b)
T1
T2
(c) (i)
(ii)
(iii)
6.7 or 6.67
–5.1 or –5.13
4.5 or 4.55
–3.8 or –3.75
3.0 or 3.03
–2.8 or –2.75
2.0 or 2.00
–2.1 or –2.06
1.5 or 1.52
–1.8 or –1.75
1.1 or 1.11
–1.5 or –1.50
Additional Guidance
Must be negative.
Allow a mixture of significant figures.
T1 and T2 must be table values.
Ignore “–” omissions.
U1
From ± 0.3 or ± 0.4 to ± 0.1 or ± 0.2
Allow more than one significant figure.
G1
Six points plotted correctly
Must be within half a small square.
Penalise “blobs”.
Ecf allowed from table.
U2
Error bars in V / E plotted correctly
All error bars to be plotted. Must be
accurate to less than half a small
square.
G2
Line of best fit
If points are plotted correctly then
lower end of line should pass between
(6.4,–5.0) and (6.6,–5.0) and upper
end of line should pass between
(1.0,–1.5) and (1.2,–1.5).
G3
Worst acceptable straight line.
Steepest or shallowest possible line
that passes through all the error bars.
Line should be clearly labelled or
dashed. Should pass from top of top
error bar to bottom of bottom error bar
or bottom of top error bar to top of
bottom error bar. Mark scored only if all
error bars are plotted.
C1
Gradient of best fit line
Must be negative. The triangle used
should be at least half the length of the
drawn line. Check the read offs. Work
to half a small square. Do not penalise
POT. (Should be about –650.)
U3
Uncertainty in gradient
Method of determining absolute
uncertainty.
Difference in worst gradient and
gradient.
© Cambridge International Examinations 2014
Page 5
(iv)
(d) (i)
(ii)
Mark Scheme
GCE AS/A LEVEL – May/June 2014
Syllabus
9702
Paper
51
C2
Negative y-intercept
Must be negative.
Check substitution into y = mx + c
Allow ecf from (c)(iii). (Should be
about –0.8.)
FOX does not score.
U4
Uncertainty in y-intercept
Uses worst gradient and point on WAL.
Check method.
FOX does not score.
C3
P = R / y-intercept
= –gradient / y-intercept
Include unit [Ω] for P and R.
Do not penalise POT.
C4
R = gradient in the range 620 to 680
and given to 2 or 3 s.f.
U5
Percentage uncertainty in P
Percentage uncertainty in gradient +
percentage uncertainty in y-intercept
[Total: 15]
Uncertainties in Question 2
(c) (iii) Gradient [U3]
Uncertainty = gradient of line of best fit – gradient of worst acceptable line
Uncertainty = ½ (steepest worst line gradient – shallowest worst line
gradient)
(c) (iv) [U4]
Uncertainty = y-intercept of line of best fit – y-intercept of worst acceptable
line
Uncertainty = ½ (steepest worst line y-intercept – shallowest worst line y-intercept)
(d) (i) [U5]
Percentage uncertainty in gradient + percentage uncertainty in y-intercept
max P =
min f =
max R
max gradient
=
min y − intercept min y − intercept
min R
min gradient
=
max y − intercept max y − intercept
© Cambridge International Examinations 2014